Light density scanning device



July 23, 1968 D. 's. STOUFFER 3,393,602

LIGHT DENSITY SCANNING DEVICE Filed Nov. 22, 1963 2 Sheets-Sheet 1 W 9 *1, a; 'J

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INVENTOR. DAVID S. STOUFFER July 23, 1968 D. s. STOUFFER 3,393,602

LIGHT DENSITY SCANNING DEVICE Filed Nov. 22, 1963 2 Sheets-Sheet 2 INVENTOR. DAVID S. STOUF'FEF? United States Patent 3,393,602 LIGHT DENSITY SCANNING DEVICE David S. Stoulfer, 311 N. Niles Ave., South Bend, Ind. 46611 Filed Nov. 22, 1963, Ser. No. 325,729 5 Claims. (Cl. 8814) ABSTRACT OF THE DISCLOSURE A light density scanning device having a carriage and reflector head assembly detachably held on a track on the edge of a work table. The carriage includes a plurality of vertically and horizontally disposed magnets which are adapted to overlie in space-away relation correspondingly disposed magnetically attractable surfaces on the track. A plurality of rollers on the carriage engage the track thereby permitting the carriage assembly to freely move therealong.

This invention relates to a new and improved form of light density scanning device. More specifically, the light scanning device of the present invention employs a unique carriage and reflector head assembly demountably held on the edge of a work table in a manner which permits free traverse along the edges of the table, while insuring perfect alignment of the reflector head therewith.

The competitive aspects of modern printing operations require the printer to promise as Well as deliver a product of extremely high quality at the lowest possible cost. Accordingly, it is necessary for the printer to exercise a high degree of quality control over printed matter especially multicolor work. In order to maintain this type of control, the more up to date pressrooms are increasingly relying on reflection densitometers or light density test setups as a tool and aid in maintaining most exacting color control through subjecting test strips or samples to testing at regular intervals. The reflection densitometer may be used to effectively check the amount of ink applied to the printed sheet, or expressed another way, may be used to measure ink film thickness which, generally speaking, is an accurate measure of the color of the printed matter.

Periodically, test strips of the colors applied are run on the press being used, and checked by a reflection densitometer to measure the ink film thickness. If the result is unsatisfactory, suitable adjustments can be made to insure a proper ink film thickness which results in the proper color being presented on the finished printed sheet, and if timely accomplished, substantial rejects or wastage avoided.

In the past, the printed sheets were disposed on a work surface and a hand held reflector head was passed over the various color test strips. While this means of checking color was satisfactory When contrasted with the prior methods of visual comparison, it was unsatisfactory for a number of reasons. Among these was the failure to provide an accurate track for the reflector head and thus it was positioned over the repeating color patches in a rather haphazard manner with the obvious unsatisfactory and inconsistent results. Considerable time was consumed in making such tests under these circumstances while the high speed presses were turning out what was later discovered to be a substandard product.

The manual handling of the reflector head subjected this somewhat delicate instrument to dangers such as dropping and other forms of physical abuse which was obviously undesirable. Further problems of this nature were encountered in the actual testing of color patches, in that the inks were smeared when the densitometer was moved from one test patch to the other requiring a rerun 3,393,602. Patented July 23, 1968 of a test strip with the attendant delay. Oher disadvantages of a more minor nature were also present which served to make color testing burdensome, difficult and impaired the ability to obtain the desired highly accurate results necessary to alert the printer to minor deviations from the standard color.

The present invention relates to a light density scanning device embodying a carriage assembly adapted to ride on the edge of a work surface. An adjustable arm is pivotably mounted on the carriage assembly and extends therefrom to adjustably mount a reflector head forming a part of a reflection densitometer test setup. Suitable means is provided to permit rapid traverse of the carriage along the edge of the work surface while maintaining the reflector head in a traversing path parallel thereto. Additional means is provided to demountably hold the carriage assembly in tight engagement with the top and side portions of the work surface with out adversely affecting free movement of the carriage, or removability from the work surface should it become desirable to use the assembly elsewhere.

Distinct advantages are presented by the present invention in the form of reduction of time consumed by color testing and greater ease and accuracy in aligning the reflector head over repeating color patches to obtain better results. The adjustability of the arm enables printed matter of variable thicknesses to be tested in a manner which precludes smearing. The novel carriage due to its unique construction is completely portable and may be shifted from one work table to another to obtain unusually accurate results in checking the overall quality in black and white as well as color printing with great consistency. This is particularly important in printing jobs where the customer has spent a considerable amount of money in calling the publics attention to the fact that his products are packaged in a box of modern design employing his standard color which may, for example, be a peculiar shade of blue. Under these circumstances, a high degree of color control is required to satisfy the customer and protect any legal rights he has in his color. The present invention When properly used, will assist in maintaining the exacting standards demanded while requiring a minimum amount of time and effort on the part of the printer or his assistant. Further advantages of the present invention will become readily apparent from a perusal of the objects and description of the present invention to follow.

It is an object of the present invention to provide a new and improved light density scanning device.

It is a further object of this invention to provide a new and improved light density scanning device embodying a reflector head coupled to an AC. amplifier with a novel carriage supporting the reflector head to permit rapid scanning of printed material.

It is a further object of this invention to provide a light density scanning device employing a unique carriage adapted to carry a reflector head thereon, with the carriage being mounted to allow traversing of the reflector head across the work surface in a path corresponding to the path generated by the guiding edge of the work surface.

It is a further object of this invention to provide a novel carriage having magnetic means to hold it in alignment with the side and top edges of a work surface including anti-friction means to allow the carriage to be easily moved along the edge of the work surface while maintainingg an arm carried thereby in precise angular alignment with the edge of the work surface.

It is a still further object of this invention to provide a new and improved light scanning device employing a carriage assembly which is held in free rolling movement to the edge of the work surface which will adjustably sup port a cantilevered arm portion carrying a reflector head together with the provision'of suitable means to maintain the reflector head in spaced relation to the work surface in the absence of external forces.

It is a still further object of this invention to provide a new and improved light density scanning device which will obviate any smearing of test color patches.

Further and fuller objects of the invention will become readily apparent when reference is made to the accompanying drawings wherein:

FIG. 1 is a perspective view of an easel supporting a color test strip with the light density scanning device of the instant invention in the operating position;

FIG. 2 is an enlarged fragmentary perspective view of a reflector head and the carriage assembly supporting the same;

FIG. 3 is an enlarged elevational view in section of the reflector head of FIG. 2;

FIG. 4 is an enlarged bottom plan view of the carriage of FIGS. 1 and 2 with the arm portion shown fragmentarily;

FIG. 5 is a fragmentary side elevational view of the carriage assembly of FIG. 2 with the track and work surface shown in section;

FIG. 6 is a cross sectional view taken along the lines 6-6 of FIG. 2.

The light density test setup indicated by the reference character 10 in FIG. 1 employs a Work surface 11, which in the present case is an easel. It is to be understood that any generally planar surface of any particular shape may be employed and when the term work surface is used, it is to be understood that it includes tables, easels and the like. At the upper edge of the work surface 11, a track 12 is provided having a pair of stop members 31 and 32 at opposite ends to prevent the carriage from accidentally running oflf the track 12. It is contemplated that one of the stop members 31 or 32 may be pivoted for purposes to become apparent.

The scanning device indicated generally at 13 utilizes a carriage assembly 23 having an arm 14 projecting therefrom to carry a reflector head 15 which is positioned over a test strip having a series of color patches adjacent one edge. A multi-wire conductor 26 leads from the reflector head 15 to an AC. amplifier which is provided with calibration and adjustment knobs 29 and 30, as well as a direct reading meter 28. As the carriage assembly 23 is moved, the reflector head 15 carried thereby is moved across the test strip 25 and changes in ink thickness will become apparent by changes in the position of the needle of the direct reading meter 28. A more complete description of this operation will be given after a description of the components.

Referring now to FIG. 2, the carriage 23 has a hinge means 22 at the outside edge thereof which pivotably supports a cantilevered arm 14. The carriage 23 is supported for movement along a magnetically attractable track 12, however, it is to be understood that any magnetically attractable surface which is substantially planar will sufiice. The arm 14 is provided with a bracket 16 having a thumb screw 17 to allow longitudinal adjustment of the reflector head 15 with respect to the carriage assembly 23. As illustrated, the reflector head 15 is positioned over a test strip 18 having a repeating series of color patches 19, 20 and 21 thereon. An adjustment means 24 to be described in detail controls the upward pivoting movement of the arm 14 so that it will remain spaced with respect to the test strip 18 in the absence of external force.

The car-riage 23 may be rolled to a position which aligns the reflector head 15 with the appropriate color patch and manual force applied to the bracket 16 or arm 14 to bring, the reflector head into engagement with the test strip. The particular reading on the meter may be observed, the reflector head released, and the carriage may be rolled to the next patch of like color where the operation is repeated. Each of the individual colors is checked completely across the strip, then the remaining colors in the same sequence.

The enlarged cross sectional view of FIG. 3 illustrates the reflector head 15 as including a housing 37 which, as shown, is split to allow access thereto. An angulated stepped bore 38 is provided within the housing and has a light source 39 at one end thereof mounted by means of a light mounting bracket 40. At the opposite end of the stepped bore 38 a pair of double convex lenses 41 and 42 are provided to collect the light rays emitted from the source 39 and project them through the opening 36. A second bore 43 is perpendicular to the underside of the reflector head 15 and also at an angle of exactly 45 to the axis of first bore 38. A pair of double convex lenses 45 and 46 are provided in the central portion of the second bore 43 along with a pair of fixed apertures 48 and 49 positioned above the lenses 45 and 46, with the lowermost fixed aperture 48 having a filter 50 associated therewith. The lense, filter, and aperture arrangement serve to distribute the :proper color of light evenly over the cathode of a photoelectric cell 47 which is positioned over the bore 43. The aperture 48 and associated filter 50 are mounted on a filter selector knob 52 which is rotatably supported by a shaft 53. Several filters are carried Within the filter selector knob being angularly spaced to allow rotation to a point where they will be in precise alignment with the axis of the bore 43.

The filters are primarily used to cancel out color insofar as the photocell is concerned. They may be complimentary or opposite in order that the photocell may only see shades of gray, which is directly proportional to the amount of ink applied to the paper by the press. Light level changes detected by the photocell are transmitted through the multi-wi-re conductor 26 to the high gain A.C. amplifier shown at 27 in FIG. 1 in order that the optical density or percent of reflectance may be read directly.

The reflection densitometer may be calibrated either in percent of reflectance or optical density depending on the choice of the user. When it is calibrated in terms of reflectance, the paper on which the light from which the source 39 is projected, and reflected to the photocell 47 is assumed to be reflective. If the meter is of the center scale zero variety, adjustment is made to maintain the needle directly over zero. When the head is positioned over a film of ink, a portion of the light is absorbed with such change in reflectance being readily discernabile on the meter. For example, after passage through the ink film, reflection off the paper and second passage through the film, 50% of the light will be reflected (Where 100% would he reflected from the unprinted paper). Accordingly, the optical density would be said to be 0.3. Generally speaking, the thicker the film of ink the less light that it reflects and accordingly the darker the color will appear to the human eye.

It is particularly important that the light source 39 be arranged at an exact angle of 45 with respect to the central axis of the bore 43 which leads to the photocell 47. In addition, the test strip contacting surfaces 44 must allow the head to be brought down into contact with the strip while the terminal portion of the bore 43 is spaced from the color patch in order to be at the apex of the angle formed by the light transmitted and reflected. Under this arrangement, wet or tacky color patches may be tested without fear of smearing.

It is to be appreciated that it is necessary to maintain careful control over the positioning of the scanning device throughout the test. Each test patch should be tested in approximately the same spot as the preceding patch in order to accurately ascertain changes in ink thickness from one side of the press to the other. Such careful control and accuracy can be readily exercised with the carriage assembly 23 shown in FIGS. 46, which includes a rigid support plate 58 joined at its rearward edge to a vertical support plate 59 by any suitable means of fastening. The hinge 22 is provided with a central pintle 64 which is received in a suitable aperture in the cantilevered arm 14 to support the reflector head 15.

Magnetic means is provided to hold the carriage to the magnetically attractable track 12, by positioning a series of permanent magnets 71, 72, 73, and 74 on the under side of the support plate 58. A backing plate 81 and a series of spacers 82 maintain permanent magnets 71-74 aflixed to the support plate 58 in spaced relation thereto. Since the upper surface of the track 12 is of magnetically attractable material, the magnets draw the plate 58 towards the track, however, a series of roller assemblies, indicated generally at 60, maintained the magnet in controlled spaced relationship to the upper surface of the track 12.

In a similar manner, a series of magnets 75, 76, 77 and 78 are provided with a backing plate 79 and series of spacers 80 which permit mounting on the vertical support plate 59 so as to overlie the side edge 83 of the track 12 or work surface 11 in the absence of a track. A pair of roller assemblies, indicated generally at 61, are disposed wit-h their rotatable axes at right angles with respect to the roller assemblies 60 so they may ride on the side edge 83 of the work surface to maintain the permanent magnets 75-78 slightly spaced therefrom.

The roller assemblies are of uniform construction and employ a generally U-shaped bracket 62 having a Wheel or roller 63 rotatably carried thereby. Any suitable form of anti-friction means may be used so long as it will maintain the permanent magnets in controlled spaced relationship with respect to the associated surface. Weight means could be used to maintain the rollers in engagement with the track.

The enlarged cross sectional view of FIG. 6 illustrates an adjustment means 24 which permits adjustment of the spacing between the reflector head and the work surface. As seen in FIG. 6, the adjustment means 24 comprises a manually operable thumb screw head 67 terminating in a collar 35 which is integral with a slender elongated shaft member 68. Shaft member 68 extends through a pair of apertures in the arm 14 to be threadably received in an adjustable nipple 69 carried by the support plate 58. The adjustable nipple 69 is provided with an internal cylindrical bore 34 to house one end of a biasing spring 70 which continually urges the arm 14 upwardly into engagement with the underside of the collar 35. The angularity of the arm 14 may be adjusted with respect to the pintle 64 by manually grasping the thumb screw 67 and rotating it either clockwise or counterclockwise. Such adjustment will allow the reflector head 15 to be maintained in the desired spaced relationship with respect to the work surface 11 and readily compensates for the diverse thickness of test strips.

In order to prevent any lateral swing of the arm 14, a guide pin 65 is carried by the arm 14 for guiding cooperation With an aperture 66 formed in the support plate 58. This insures that the reflector head will travel in a true vertical plane when force is applied to bring it into contact with test patches disposed on the Work surface 11. Obviously, proper alignment is necessary to obtain accurate test readings.

The carriage assembly described above allows most accurate positioning of the reflector head 15 due to its ability to be rolled easily along the edge of the work surface. Although it is moved quite easily along the edge of the work surface, consider-able force would have to be exerted to overcome the force of the magnets in order to remove it therefrom, since the carriage assembly takes advantage of the known principle that lines of magnetic force are more easily broken in shear than in tension. Either or both of the stop members 31 and 32 may be pivoted to allow the carriage assembly to be rolled off the end of the work table 11 in order that it may be transported elsewhere to be used in conjunction with other Work surfaces. Obviously, the particular shape or positioning of the work surface is relatively unimportant since the carriage holding forces are exerted in two directions by the permanent magnet on the carriage assembly. Accordingly, the only requirement is that the edge of the work surface be magnetically attracta'ble and substantially planar in order for the roller assemblies 60' and 61 to maintain the associated magnets in spaced relation with respect thereto to enhance the free movability thereof. It is obvious that various other uses may be made of the carriage assembly where precision alignment of an arm is of utmost importance and especially those applications where external forces. are likely to be applied to the arm.

The operation of the light density scanning device will now be explained with particular reference to FIGS. 1-3. The amplifier, carriage assembly and reflector head are positioned as shown with the customers standard colors aligned with the edge of the work surface. The reflector head with the light source energized and a blue filter over the bore 43 is moved to an unprinted area of the paper or board being printed. A light downward force is applied to the reflector head to bring the strip contacting buttons 44 into engagement with the test strip. The meter is adjusted to read reflectance or zero (0) optical density. The carriage assembly is then rolled to each of the customers standard color patches and the readings thereof noted in a similar manner. With the level of reflectance or optical density of the standard colors noted, test strip samples are taken at regular intervals from the press, and checked as will be described below to insure conformance with the customers standard colors, the density of each having been noted in the manner described above.

The test strip 18 is placed on the work surface 11 with the color patches aligned parallel to the edge of the work surface. Suitable means such as register pins, three point register guides, or the like may be provided to expedite the positioning of the test strip. The reflector head is moved to one of the color patches, for example, either the process magneta, process cyan or process yellow, indicated at 19, 20 and 21 respectively. Each color is checked completely across the strip with the appropriate filter in the reflection head and any variation from thest-andard color reading is noted. Suitable adjustments of the ink fountain keys on the press may be immediately effected to correct any deviations of the test strip colors from the standard readings noted.

The carriage assembly permits rapid traverse across the test strip with the added assurance that each color patch will be checked in the same relative location to obtain uniformly accurate results. The printer or his assistant only needs to align the reflector head in the transverse direction since once positioned, the reflector head will track accurately in a longitudinal direction throughout the test. The reflector head is manually forced into contact with the test strip with the spaced test strip contacting buttons 44 preventing direct contact with ink thus preventing .smearing which could affect the reading taken. The magnetic means mounting the carriage to the work surface are of sufficient strength to resist the forces applied to the reflector head. The reflector head is then released and the biasing spring forces the arm 14 upward so that during lateral movement to the next color patch the reflector head will remain spaced from the strip. As previously noted, any variation in material thickness may be compensated for by the adjustment means to control the upward swing of the arm 14. Checks of this nature may be made from hour to hour during the press run to maintain color consistency and uniformity of all the subject matter printed. This high standard of control may even be maintained in those printing operations which are on a multiple shift basis, since the night crew will be able, through the use of the light density scanning device described above, to see the color as well as the day time and afternoon crews.

. While the foregoing invention has been described in connection with but a single embodiment, it is not intended that this be limiting inasmuch as the illustrations and language employed in describing the invention was chosen to present a clear description of the device. It is obvious that various modifications may be made Without departing from the inventive concepts embodied herein and therefore, it is intended that any limitations imposed be within the spirit and scope of the appended claims I claim:

1. A light density scanning device comprising a carriage to be mounted on a surface, said carriage having a pivoting arm projecting from a first side thereof, a reflector head slida-bly mounted on said arm, said reflector head including a light source and photocell having the fields of projection and view arranged at an angle to each other, amplifier means electrically connected to said photocell, means supporting said carriage for linear movement along said mounting surface, said supporting means including first magnetic means carried by said carriage and overlying a first magnetically attractable part of said mounting surface in spaced relation thereto, second magnetic means mounted on said carriage and being adapted to overlie a second magnetically attractable part of said mounting surface in spaced relation thereto, said first and second magnetically attractable parts of said mounting surface being angularly disposed to each other, and antifriction means to support said carriage, said anti-friction means being adapted to hold said magnetic means in spaced relation to said first and second magnetically attracta'ble parts of said mounting surface.

2. A light density scanning device particularly adapted to check optical density of printed material comprising a carriage having a cantilevered arm supported thereby, a reflector head carried by said arm, said reflector head including a light source and photosensitive means, means shifta-bly holding said carriage on a work surface, said work surface including a top portion terminating in an angularly positioned edge, a magnetically attractable material overlying at least a part of said angularly positioned edge and top portion of said work surface, said holding means including first magnetic means overlying said top portion of the work surface, anti-friction means maintaining said first magnetic means in controlled spaced relation to said top portion of said work surface, second magnetic means overlying said angularly positioned edge of said work surface and anti-friction means maintaining said second magnetic means in controlled spaced relation to said edge while permitting free movement parallel to said edge.

3. A light density scanning device comprising a reflector head, said reflector head including a light source and photosensitive means, an arm supporting said reflector head, a carriage assembly supporting said arm for free movement of said reflector head across a work surface, said work surface being adapted to support a printed test strip, said carriage having a first magnetic means to hold said carriage in spaced relation to a top portion of a work surface and a second magnetic means to hold said carriage in spaced relation to a side edge of said work surface, anti-friction means for maintaining said carriage in spaced relation from said work surface, each of said first and second magnetic means cooperating with said antifriction means which engage said work surface, thereby permitting movement of said carriage along said work surface while maintaining said carriage in spaced relation to said surface.

4. The light density scanning device of claim 2 further including hinge means on said carriage supporting said arm, and means to maintain said arm and reflection densitometer in spaced relation to said work surface in the absence of external forces.

5. The light density scanning device of claim 4 wherein guide means is provided on said arm intermediate said hinge means and said reflection densitometer to maintain said arm at right angles with respect to said carriage and said Work surface edge.

References Cited UNITED STATES PATENTS 3,201,182 8/1965 Weissman 308--10 3,272,568 9/1966 Koorneef et a1.

3,053,181 9/1962 Jorgensen 8814 X 3,019,693 2/1962 Patnode 88-14 2,947,232 8/1960 Armentrout et a1. 88-14 X 2,773,412 12/1956 Huck 88-14 JEWELL H. PEDERSEN, Primary Examiner.

W. A. SKLAR, Assistant Examiner. 

